bibliography * The PainScience Bibliography contains plain language summaries of thousands of scientific papers and others sources, like a specialized blog. This page is about a single scientific paper in the bibliography, Vachon-Presseau 2018.

PainSci summary of Vachon-Presseau 2018?This page is one of thousands in the PainScience.com bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided at the bottom of the page, as often as possible.★★☆☆☆?2-star ratings are for studies with flaws, bias, and/or conflict of interest; published in lesser journals. Ratings are a highly subjective opinion, and subject to revision at any time. If you think this paper has been incorrectly rated, please let me know.

This trial claims to have found evidence of psychological and neurological traits that predict the potency and duration of placebo response. It’s garbage, a terrible study and a terrible paper. It seems to bizarrely prides itself on using a no-treatment group when this is clearly a poor choice, highly subject to a “frustrebo” effect. It is far too small a study, to underpowered, to actually detect a correlation between such squishy things as psychological traits and placebo response. The authors exhibit an egregious placebo-hype bias in their public statements and in the paper itself, and their methodology has a huge amount of “wiggle room” for p-hacking and rampant methodological flexibility. And there’s more.

original abstract†Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

The placebo response is universally observed in clinical trials of pain treatments, yet the individual characteristics rendering a patient a 'placebo responder' remain unclear. Here, in chronic back pain patients, we demonstrate using MRI and fMRI that the response to placebo 'analgesic' pills depends on brain structure and function. Subcortical limbic volume asymmetry, sensorimotor cortical thickness, and functional coupling of prefrontal regions, anterior cingulate, and periaqueductal gray were predictive of response. These neural traits were present before exposure to the pill and most remained stable across treatment and washout periods. Further, psychological traits, including interoceptive awareness and openness, were also predictive of the magnitude of response. These results shed light on psychological, neuroanatomical, and neurophysiological principles determining placebo response in RCTs in chronic pain patients, and they suggest that the long-term beneficial effects of placebo, as observed in clinical settings, are partially predictable.